Yggdrasil-jumper

This project aims to transparently reduce latency of a connection over Yggdrasil network for such applications as online gaming, VoIP and others.

How it works

By default, yggdrasil-go routes data only through explicitly connected peers and doesn't attempt to reach other nodes accessible over the internet. Therefore, path usually contains 1-2 intermediary nodes, namely public peers of both sides. If both you and your peer use internet, you can send traffic directly (aka peer-to-peer), thus reducing latency.

• Jumper connects to Admin API of the running router. And monitors active sessions (peers you have data exchange over Yggdrasil network with).
• Once any such session appears, jumper tries to connect to associated peer, assuming it has another jumper running on the same listen_port.
• Both jumpers exchange their external internet addresses and use NAT traversal technique to instantiate direct bridge over the internet.
• If previous step was successful, jumper will relay all data passing the bridge to the router until session is closed or other error occurs.

Usage

Jumper can run without additional configuration. All it needs is access to Admin API of the router and to the IP network.

$ yggdrasil-jumper --loglevel info # off/error/warn/info/debug
...

It may be helpful to know what the defaults are.

$ yggdrasil-jumper --print-default
...
# List of possible admin socket locations
yggdrasil_admin_listen = [
  "unix:///var/run/yggdrasil/yggdrasil.sock",
  "unix:///var/run/yggdrasil.sock",
  "tcp://localhost:9001",
]
...
# List of yggdrasil listen addresses
# Connect to one, instead of using `add/removepeer` commands
# Noteworthy, this is the only way to use routers prior to v0.4.5 (Oct 2022)
yggdrasil_listen = [ ]
...
# List of allowed yggdrasil peer addresses
# Uncomment to apply
#whitelist = [ ]
...
# Default connect/listen port in yggdrasil network
listen_port = 4701
...
# List of STUN servers
stun_servers = [
  ...
]
...

You can also overwrite some if needed.

$ yggdrasil-jumper --config <path> # standard input will be read if path is "-"
...

Installation

• Downloading: Check the Releases page.
• Compiling:

  $ git clone https://github.com/one-d-wide/yggdrasil-jumper
  $ cd yggdrasil-jumper
  $ cargo build --bin yggdrasil-jumper --release
  $ sudo cp target/release/yggdrasil-jumper /usr/local/bin/yggdrasil-jumper

Details

External address lookup

In order to know what address to use with NAT traversal, jumper must know self external internet address and port. This task is performed using STUN protocol with TCP extension, hence not every STUN server is supported. STUN standard is quite broad, but jumper utilities only address lookup feature.

You can check compatibility using stun-tcp binary from this repository.

$ cargo build --bin stun-tcp --release
$ # ./target/release/stun-tcp

stun-tcp takes STUN server(s) as argument and outputs resolved address.

$ stun-tcp --print-server stunserver.stunprotocol.org:3478
stunserver.stunprotocol.org:3478 244.13.30.107:28674

You can also take servers from hardcoded defaults or your configuration.

$ stun-tcp --default
244.13.30.107:28674
...

If stun-tcp fails to connect to any server it will print error and exit with code 1.

$ stun-tcp stunserver.stunprotocol.org:3478 [::]:0
244.13.30.107:28674
ERROR While resolving {server=[::]:0}: Failed to connect: Connection refused

It also checks whether all servers return same address. You can skip this check by passing --no-check argument.

$ stun-tcp stunserver.stunprotocol.org:3478 wrong.resolver
244.13.30.107:28674
ERROR While resolving {server=wrong.resolver}: {received=0.0.0.0:0}: Previously resolved addresses do not match

Establishing direct connection over the internet

You can read more about the procedure in this paper.

• Create and bind listen and connection sockets to the same port (using SO_REUSEADDR and SO_REUSEPORT flags).
• Lookup self external address and port.
• Exchange external addresses with peer.
• Try to connect to the peer and listen for connection simultaneously.

Improvements since prototype

The overall pipeline is mostly the same. The most notable improvements are:

• Efficient concurrent multitasking.
• Robust error handling.
• Sane user interface and logging.
• Support of older routers.
• Firewall traversal at address exchange phase.